Direct in vivo treatment of established MDA-MB-468 tumors. Tumors were injected with H5.110hIFNβ at 3 × 109 pfu (•), 1 × 109 pfu (■), 3 × 108 pfu (○), 1 × 108 pfu (▵), and 3 × 107 pfu (▿), respectively, or with PBS (□), or with H5.110lacZ at 3 × 109 pfu (⊠), 1 × 109 pfu (◊), 3 × 108 pfu (▴), and 1 × 108 pfu (▹), respectively. Tumor sizes were measured over 14 days after the treatment injections.